Mobile phones have become important devices in our daily life. A mobile phone or device is generally a subscriber to a telecommunication network in order to enjoy communication services, such as voice, data, . . . . A mobile user is generally identified using an International Mobile Subscriber Identity, or IMSI. The mobile IMSI is a unique number associated with all GSM (Global System for Mobile communications) and Universal Mobile Telecommunications System (UMTS) network mobile phone users. It is stored in the Subscriber Identity Module (SIM) inside the phone. The SIM is actually unique to one subscriber and carries information to identify that subscriber in his home network, i.e. the network he is a subscriber of. This information includes the IMSI, further authentication data, and other data. The SIM is generally provided by the network operator when a user gets his subscription, and corresponds on this network to a unique MSISDN (Mobile Station International Subscriber Directory Number) which is actually the mobile device phone number in this network.
With the success of mobile telephony, and more generally with the multiplicity of enhanced communication services, each user today ends up associated with more than one communication devices, and consequently as many phone numbers—home, work, mobile, . . . .
Several recent developments have appeared to easy the user's burden in handling his numerous devices and/or phone numbers.
SIM cards carrying multiple subscriber identities are now available. Users can switch between subscriber identities using one single mobile device to register with different networks. One downfall with such a solution is that the user still has as many phone numbers as existing subscriber identities in his SIM card. Furthermore, as only one subscriber identity can be active at a time, call forwarding solutions are needed when a call involves the MSISDN of an inactive subscriber identity, i.e. an inactive MSISDN. For instance, when the user with multiple subscriber identities places a call to a recipient device using one of his inactive MSISDNs, a complex solution will be needed to use this inactive MSISDN as the caller Identification (CID).
Presenting the Caller Identification is a fairly recent service provided by most if not all network operators to their subscribers. For instance Caller ID (CID) corresponds to the service offered the PSTN (Public Switched Telephone Network). CLIP (Calling Line Identification Presentation), a similar service offered for GSM mobile devices, is described in the document 3GPP (3rd Generation Partnership Project) TS23.081. Different solutions are available to transmit the caller ID information to the recipient device, for instance an SS7 (Signaling System 7) message for PSTN lines or an SIP (Session Initiation Protocol) message setup in GSM and UMTS networks for Voice over IP. The presented Caller ID is generally the subscriber Caller ID, here after referred to as the default Caller ID.
Changing the Caller ID for a calling device would allow to manage multiple Caller IDs through only one device. A user could place a call using his office, mobile, home, . . . called ID without the need of all the corresponding devices.
Solutions are known to present to a recipient device a Caller ID different than the default Caller ID. US2007105531S discloses a mobile device with a single SIM—and corresponding MSISDN—that is allocated with other MSISDNs. The mobile device, when sending a call setup message for calling a recipient device, passes on its IMSI number for authentication as well as one of the allocated MSISDN as the caller ID. As the call setup message is sent to the MSC (Mobile Switching Center), the MSC must support this additional parameter, and be modified accordingly. This additional field is not provided in the existing standards, and such a modification would require a heavy reconfiguration of all MSCs to be supported.
Today there is still a need for a simple solution that allows an efficient management of a user's plurality of Caller IDs. There is a further need for a service continuity when a user with multiple Caller IDs receives a call.